The present invention relates to a correction method for correcting television signals transmitted in blocks by detecting a defective block with the use of an error detection circuit and reducing the effect of errors in the defective block with an error concealment circuit which is activated by the error detection circuit when a defective block is detected.
The article entitled, "Channel Error Recovery for Transform Image Coding" in IEEE Transactions on Communications. Vol. COM-29, No. 12, December 1981, introduces an error reduction method of two-dimensional transform image coding. Arbitrarily or systematically selected television picture sections are identified as blocks. Before transmission, the blocks are transformed into spectral blocks and coded. After transmission, spectral blocks are decoded and retransformed. Defective blocks are detected and corrected by utilizing the natural redundance in a television picture. Natural redundance results from the fact that generally a block does not have greater changes in brightness and/or color at its interfaces with all adjacent blocks. If, in the decoded signal which serves as a measure for the brightness and/or color of the picture content, greater changes in brightness and color exist at all edges of a block, this indicates a transmission error and correction information can be calculated from the differences at the block interfaces and used to subsequently correct the block.